1. Field of the Invention
The present invention relates to a semiconductor device including a capacitor having an MIM (Metal-Insulator-Metal) structure and a method of manufacturing the same.
2. Description of Related Art
A capacitor (hereinafter referred to as “MIM capacitor”) having a structure (MIM structure) obtained by sandwiching an insulating capacitor film between a lower electrode and an upper electrode exhibits a small resistive component, and can be increased in capacitance density. Therefore, the MIM capacitor has drawn attention particularly as a capacitor loaded on a system LSI for a radio communication.
While the lower electrode and the upper electrode of the MIM capacitor are generally formed by metal films containing Al (aluminum), it is attempted to apply Cu (copper) having higher conductivity than Al to the material for the lower electrode in place of Al, in order to further reduce the resistance.
FIG. 3 is a schematic sectional view of an MIM capacitor employing Cu as the material for a lower electrode.
This MIM capacitor 91 is formed on a semiconductor substrate (not shown) through an interlayer insulating film 92. A lower electrode 93 made of Cu is embedded in a trench formed on the surface layer portion of the interlayer insulating film 92 by the so-called damascene process. The surface of the lower electrode 93 is generally flush with the surface of the interlayer insulating film 92, and a capacitor film 94 made of SiN (silicon nitride), for example, is stacked on the surfaces of the interlayer insulating film 92 and the lower electrode 93. An upper electrode 95 is made of TiN (titanium nitride), for example, is in the form of a flat plate smaller in size than the lower electrode 93 in plan view, and is opposed to the lower electrode 93 with the capacitor film 94 sandwiched therebetween.
Another interlayer insulating film 96 is stacked on the capacitor film 94 and the upper electrode 95. A lower electrode contact plug 97 and an upper electrode contact plug 98 are provided to penetrate the interlayer insulating film 96 in the thickness direction. The lower electrode contact plug 97 further penetrates the capacitor film 94, and the lower end thereof is connected to the lower electrode 93. The lower end of the upper electrode contact plug 98 is connected to the upper electrode 95.
In a semiconductor device loaded with an MIM capacitor having such a structure, however, the MIM capacitor occupies a wide area on a semiconductor substrate, to hinder downsizing of the semiconductor device.